The present invention relates to a side sliding door apparatus that opens and closes a side entrance of a vehicle such as an electric railcar.
As the side sliding door apparatus is entrusted with the lives of the passengers, it must not open arbitrarily from a condition in which the doors are closed, regardless of whether the vehicle is in motion or stationary, and it must consistently be maintained in a closed position by a constant pressure in order to prevent the ingress of rain water or wind, to prevent vibration while in motion, and the like. However, it must be easily unlock the apparatus by a manual operation when an emergency situation such as a power cut occurs, the vehicle stops, and the passengers escape from the vehicle. Because of the above points, a high operational reliability is required for the side sliding door apparatus for vehicle. The present inventor has developed a side sliding door apparatus for vehicle that meets this requirement, for which the present inventor has previously filed patent applications (refer to JP-A-2000-142392 and JP-A-2002-038786). The previous invention improves one portion of the side sliding door apparatus for vehicle.
FIGS. 4 to 7 show the side sliding door apparatus for vehicle according to JP-A-2000-142392, and a simple description will be given thereto. FIG. 4 is a front view showing the entire side sliding door apparatus for vehicle, and FIG. 5 is an enlarged view of a main portion thereof. In FIGS. 4 and 5, two sliding doors 1 and 2 are suspended movably by means of movable bodies 4 from a door rail 3 attached horizontally along the side of a vehicle; move in mutually opposing directions to the left and right of the drawings; and open and close the vehicle entrance. The sliding door 1 on the left side of the drawings is driven by a linear motor 5 acting as an actuator coupled to the movable body 4 of the sliding door 1 but, as shown in FIG. 5, a mover 5a of the linear motor 5 is engaged so as to be slidable with respect to the movable body 4 for a certain distance x in the opening and closing directions (the left and right directions in the drawings), and a compression spring 6 is inserted between the mover 5a and movable body 4. That is, the linear motor 5 is coupled to the sliding door 1 so as to be movable for the certain distance x relative to the opening direction of the sliding door 1.
Meanwhile, the sliding door 2 on the right side moves in conjunction with the sliding door 1 via a direction converting mechanism 7. As shown in FIG. 5, the direction converting mechanism 7 comprises a lower rack 9 coupled to the movable body 4 of the sliding door 1 via a coupling rod 8, an upper rack 11 coupled to the movable body 4 of the sliding door 2 via a coupling plate 10, and a pinion 12 that meshes with the racks 9 and 11 simultaneously. The lower rack 9 and upper rack 11 are slidably guided in the opening and closing directions inside a unit case 7a fixed to the vehicle side, and the pinion 12 is supported by a fixed shaft. The direction of the opening and closing movement of the sliding door 1 driven by the linear motor 5 is converted by the direction converting mechanism 7, and the conversion conveyed to the sliding door 2.
FIGS. 6 and 7 show a sliding door locking mechanism 13 installed together with the direction converting mechanism 7, and a push fitting 14 and pull fitting 15 that lock and unlock the sliding door locking mechanism 13, wherein FIG. 6 represents a condition when locked and FIG. 7 a condition when unlocked. In FIGS. 6 and 7, the push fitting 14 and pull fitting 15 are attached to the leading end of the mover 5a of the linear motor 5. The push fitting 14 is rod-shaped and is fixed horizontally at one end, and the pull fitting 15 with a hook-shaped leading end is placed on the upper surface of the push fitting 14, and joined by a pin at the base end portion to the push fitting 14 in such a way as to be able to turn in a vertical direction. The pull fitting 15 is biased in an upward direction by a compression spring 16 inserted between the pull fitting 15 and push fitting 14, while a turning in the upward direction is restricted by a headed pin 17 loosely penetrating the push fitting 14 and screwed into the pull fitting 15. Also, a guide fitting 18 that comes into contact with the upper surface of the pull fitting 15 and restricts the upward turning thereof is attached to the leading end of the fixed portion of the linear motor 5.
Next, the locking mechanism 13 comprises a slider 19 slidably guided in the direction of movement of the sliding doors 1 and 2, a back spring 20 formed by a compression spring that biases the slider 19 in the closing direction (leftward in FIG. 6) of the sliding door 2, a latch 21 slidably guided up and down, and a lock spring 22 formed by an extension spring that biases the latch 21 in a downward direction. A cam surface 19a formed by an inclined stepped surface, as shown in the drawings, is formed on the upper surface of the slider 19, and an engagement portion 19b is provided on the leading end of the slider 19.
Although not shown in detail, the latch 21 comprises a vertical latch rod 24 guided so as to be movable up and down in a guide tube 23 fixed to and supported by the unit case 7a, and a frame 25 integrated with the latch rod 24, and a roller 26 that comes into contact with the cam surface 19a formed on the slider 19 is turnably attached to the frame 25. The lock spring 22 that biases the latch 21 in a downward direction is stretched between the frame 25 and unit case 7a. 
FIG. 6 is a condition of this kind of side sliding door apparatus wherein the sliding doors 1 and 2 are closed, and locked in the closed condition. That is, in this condition, the roller 26 drops onto the lower level surface of the stepped surface formed cam surface 19a, in conjunction with which the leading end of the latch rod 24 enters into a lock hole 27 of the upper rack 11, stopping the sliding motion of the upper rack 11. As a result of this, the sliding doors 1 and 2, which move in conjunction with the upper rack 11, cannot move, and are locked in the closed position. Also, in this condition, the push fitting 14 runs up against the engagement portion 19b of the slider 19, and the hook of the pull fitting 15 is engaged on the engagement portion 19b. 
Upon providing a sliding door opening command in this condition, the mover 5a of the linear motor 5 moves to the left. In the initial stage of this movement, the mover 5a, leaving the sliding door 1 in the closed position, moves for the certain distance x to the left while compressing the compression spring 6, at which time the slider 19 is pulled by the pull fitting 15 via the engagement portion 19b. At this time, the pull fitting 15 tries to open upward, but cannot open as it is held down by the guide fitting 18.
Herein, when the slider 19 is pulled and moves to the left, as shown in FIG. 7, the roller 26 is pushed along the inclined surface of the cam surface 19a up onto an upper level surface (an approximately horizontal surface) 19c thereof. Because of this, the latch 21 is lifted up, the latch rod 24 comes out of the lock hole 27, the locking of the upper rack 11 is released, and the sliding doors 1 and 2 are also unlocked. Meanwhile, on the movement distance of the mover 5a reaching approximately x, the holding down of the pull fitting 15 by the guide fitting 18 is stopped. As a result of this, the pull fitting 15 turns upward owing to the action of the compression spring 16, and is released from the engagement portion 19b of the slider 19. Even after the pull fitting 15 is released, the slider 19 stays in the advanced position owing to the action of the back spring 20, and the roller 26 is held in the condition in which it is pushed up onto the upper level surface 19c of the cam surface 19a. 
After that, when the mover 5a moves the sliding door 1 in the leftward direction as far as a predetermined open position, the sliding door 2 also moves in a rightward direction via the rack and pinion mechanism (refer to FIG. 5). By this happening, the opening operation of the sliding doors 1 and 2 is completed. Subsequently, when the sliding door 1 moves in the rightward direction, driven by the actuator in response to a closing command, and eventually reaches the closed position of FIG. 6, the mover 5a pushes the slider 19 to the right via the push fitting 14. As a result of this, the roller 26 drops from the upper level surface 19c of the cam surface 19a, so that the latch rod 24 falls, and enters the lock hole 27 of the upper rack 11. By this means, the locking of the sliding doors 1 and 2 by the latch 21 is carried out.
Although the opening, closing, and locking of the sliding doors 1 and 2 are carried out as heretofore described, a locking detection switch 28 is provided in order to detect whether or not the locking is completed. A magnetic proximity switch is used for the locking detection switch 28, wherein a magnet element 28a formed by a permanent magnet is attached to the frame 25 of the latch 21, and a contact element 28b incorporating a reed switch is attached to the unit case 7a. The locking detection switch 28 is such that, in the locked condition of FIG. 6, a locking completed signal ON is transmitted by the magnet element 28a approaching the contact element 28b, and in the unlocked condition of FIG. 7, an unlocking OFF signal is transmitted by the magnet element 28a rising away from the reference position of the contact element 28b. At a time of an emergency release, the latch 21 is pulled up and unlocked by a wire 30 by a handle 29 shown in FIG. 4 being rotated 90 degrees, but this configuration is omitted from the drawing. Refer to JP-A-2000-142392 for details of the side sliding door apparatus for vehicle.
The heretofore known side sliding door apparatus for vehicle described above is such that there is room for further improvement of the following points.
1. When the sliding doors 1 and 2 are unlocked, the slider 19 is pushed to and held in the advanced position by the spring force of the back spring 20 in order to maintain the roller 26 of the latch 21 in the condition in which it is pushed up onto the upper level surface 19c of the cam surface 19a formed on the slider 19, but when an external force equal to or greater than the spring force is exerted on the slider 19 due to vibration of the vehicle or the like, there is a danger that the slider 19 moves in the locking direction, due to which the roller 26 drops from the upper level surface 19c of the cam surface 19a, and that for this reason the locking mechanism 13 cannot lock normally in response to the next sliding door closing command.
2. The magnetic proximity switch 28 configured of the magnet element 28a and contact element 28b is used as the locking detection switch, but the operating position differs slightly between the locking time and unlocking time due to the effect of the hysteresis of the magnet element 28a, and position setting when attaching is difficult.
Therefore, an object of the invention is to address these problems, and further increase the operational reliability of the side sliding door apparatus for vehicle by preventing malfunction due to vibration or the like.
An invention that achieves this kind of object is proposed in JP-A-2002-038786.
The invention of JP-A-2002-038786 is such that, in order to prevent malfunction due to vibration or the like, a projection that prevents the dropping of the roller of the latch at the unlocked position of the slider is formed on the upper level surface of the cam surface of the slider.
However, with the invention of JP-A-2002-038786, there is also a problem wherein, when the sliding doors 1 and 2 are unlocked, the roller 26 of the latch 24 goes beyond the projection of the upper level surface of the slider 19, and the noise caused by the impact when the roller 26 drops onto the horizontal portion of the upper level surface (the fixed position in the unlocked condition) is large compared with a case in which there is no projection.